1. Field of the Invention
The present invention relates to an engine of the type utilized to power an outboard motor, and more particularly to a fuel supply system for an engine positioned within a cowling of an outboard motor and powering a water propulsion device of the motor.
2. Description of Related Art
Fuel vapors can be problematic in the fuel-supply system for internal combustion engines, especially those of the type in which the fuel is injected with a fuel injector. Fuel vapors are unpredictable and their concentration in the fuel supply system varies. The unpredictability of the vapors causes the fuel injector to deliver fuel in a ratio to the air which may be leaner or richer than desired, resulting in poor engine performance.
Further, the fuel supply system may be used with an engine positioned in a confined space, such as the cowling of an outboard motor. In these situations, space is limited, and the fuel supply system needs to be as small and simple in arrangement as possible.
In the past, fuel-vapor separators have been provided along the fuel supply path to separate at least part of the vapor from the liquid fuel. In manifold injection systems, an electrically-operated, high-pressure pump has been positioned within the vapor separator in order to save space and to permit the pump to be cooled.
In direct injection systems, fuel is injected directly into the combustion chamber. This type of fuel injection requires that the fuel be injected at a higher pressure than with manifold injection systems, in which the injection pressure is substantially at or even below atmospheric pressure. Electric pumps are not totally capable of supplying fuel at such high pressures. Instead, a mechanical pump that is driven by the engine has been used to generate the high pressures required by direct injection systems.
In order to make the fuel distribution system more compact, the mechanical high pressure pump can be located in the vicinity of the engine""s cylinder head. Similarly, the fuel rails that deliver fuel from the high pressure pump to fuel injectors can be located close to the cylinder head. Since the cylinder head is heated by lubricating oil, it becomes very hot. As heat is transferred from the cylinder head to the fuel supply system, vapors may accumulate within the fuel rails.
A need therefore exists for a fuel supply system for a direct injected engine wherein the fuel pumps and delivery lines are arranged in a compact manner and wherein the fuel supply system prevents vapors from accumulating in fuel supply pipes that are located in the vicinity of the cylinder head.
Advantageously, the fuel supply system of the present invention is arranged to reduce the girth of the engine and to reduce the transmission of vapor to the charge former(s) of the engine. In this manner, the air/fuel ratio of the charge supplied to each combustion chamber of the engine is more accurately controlled and engine operation is improved.
In accordance with one aspect of the present invention, an engine is provided for powering an outboard motor. The engine is positioned in a cowling of the motor and is arranged to drive a water propulsion device of the motor. The engine comprises a plurality of combustion chambers arranged vertically relative to each other. Each combustion chamber communicates with a charge former. A fuel supply system includes a pump and a fuel rail. The fuel rail communicates with the charge formers and the pump has a discharge port that communicates with the fuel rail. The pump discharge port is positioned above the uppermost one of the charge formers so that any vapor forming in the fuel rail can travel upwardly to the pump.
In one form, the engine includes a pair of cylinder banks, each of which defines in part a plurality of combustion chambers arranged generally one above the other. The pump is arranged in this engine so as to be at a higher position on the engine than the uppermost one of the charge formers associated with at least one of the cylinder banks, and preferably higher than an uppermost one of all of the charge formers associated with both cylinder banks.
The fuel pump in one mode can be positioned on a top side of the engine and be driven by a crankshaft of the engine through a pulley system. In other modes, the fuel pump can be driven by a camshaft of the engine through a pulley system, through a direct axial connection, or through a cam of the camshaft.
Another aspect of the present invention involves an engine with a compact configuration that powers an outboard motor. The engine is positioned within a cowling of the motor and is arranged to drive a water propulsion device. The engine comprises a cylinder block and at least one cylinder head connected to the cylinder block. The cylinder head and the cylinder block cooperate with each other to define a cylinder bank containing at least one cylinder. Each cylinder accommodates a reciprocating piston. At least one combustion chamber is defined between the cylinder head, a wall of the cylinder, and the corresponding piston. A fuel system is provided and includes a fuel pump that communicates with a charge former through a fuel rail. The charge former communicates with the combustion chamber. The cylinder head has a recess formed along a side thereof, and the fuel rail is positioned within the recess.
In one mode, the engine has a V type configuration and further includes a second cylinder head attached to the cylinder block. The second cylinder head and the cylinder block cooperate with each other to define a second cylinder bank containing at least one cylinder. The second cylinder head, like the first cylinder head, includes a recess formed along a side thereof, and another fuel rail is received within the recess of the second cylinder head.
Further objects, features, and advantages of the present invention over the prior art will become apparent from the detailed description of the drawings which follows, when considered with the attached figures.